The distinctive five-leaf structure of a marijuana plant is seen as it grows in a medical marijuana center in Denver (Photo: Reuters)

While it may not settle the debate over how drug use begins, researchers found that alcohol, not marijuana, is the gateway drug that leads teens down the path of hard drug use, according to a new study that will be published in the August edition of the Journal of School Health.

"By recognizing the important predictive role of alcohol and delaying initiation of alcohol use, school officials and public health leaders can positively impact the progression of substance use," Adam Barry, study author and an assistant professor at the University of Florida, said in a statement.

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Researchers looked at data from over 14,500 students from 120 public and private schools in the United States to evaluate whether students had used any of 11 substances, including alcohol, tobacco, marijuana, cocaine, heroin, LSD, amphetamines, tranquilizers and other narcotics. They found that more often than not, alcohol was the first substance students tried before moving on to other drugs.

"I am confident in our findings and the clear implications they have for school-based prevention programs. By delaying and/or preventing the use of alcohol, these programs can indirectly reduce the rate of use of other substances," Barry said in a statement.

Alcohol was also the most commonly used substance, according to the study. More than 70 percent of students reported using alcohol at some point during their lifetime, compared to only 45 percent who reported using tobacco and 43 percent who used marijuana.

Researchers also found that students who used alcohol were up to 16 times more likely to use illicit drugs.

Barry said the study underlines the importance of parental roles in speaking to their child about drugs and alcohol.

"Parents should know that a strict, zero-tolerance policy at home is best. Increasing alcohol-specific rules and decreasing availability will help prevent an adolescent's alcohol use," he said. "The longer that alcohol initiation is delayed, the more likely that other drug or substance use will be delayed or prevented as well."